EP3630057B1 - Perfumes in the form of aqueous microemulsions - Google Patents

Description

The invention relates to perfuming volatile aqueous microemulsions based on the use of solvo-surfactants.

Conventionally, perfumes include, as solvents, alcohols, such as ethanol or else isopropanol. The use of these solvents presents, however, a certain number of disadvantages: they are very volatile and flammable, which involves a certain dangerousness during their production, and to a certain extent, their use. On the other hand, their own smell can interfere with that of the perfume. In addition, applied to the skin or hair, these fragrances can cause dryness, especially in consumers with sensitive skin.

We are therefore currently witnessing, for reasons in particular of public health and / or ecology, the emergence of new perfume compositions. The objective pursued is the reduction or even the elimination of volatile organic compounds (such as alcohols) contained in perfumes, by developing perfuming compositions in the form of stable aqueous solutions or dispersions.

However, most perfume molecules are hydrophobic and therefore not soluble in water. To get around this problem, it is known practice to use surfactants making it possible to dissolve the perfume molecules inside micelles forming microemulsions. It is desirable that the swollen micelles containing the perfumes are of small size so that the perfume composition has a transparent or at least translucent appearance. Thus, the production of microemulsions meeting this criterion of transparent appearance is of major interest. The document WO2014 / 090959 discloses oil-in-water type perfume microemulsions.

Other constraints are linked to the thermodynamic stability of the microemulsion, to the non-sticky nature of the latter and to the absence of residue on the skin or on the clothes. It is therefore important to be able to prepare them using as little surfactant as possible.

There is therefore a need for a stable perfuming composition, containing a large amount of perfume, which is transparent or at least translucent, and which contains as little surfactant as possible.

The object of the present invention is to provide aqueous, transparent microemulsions, substantially free of ethanol, containing at least one hydrophobic perfume substance (preferably at least 3% and preferably approximately 10% of perfume), and at least one solvo-surfactant. volatile. Such odoriferous or perfuming microemulsions are stable, and include as few substances as possible causing undesirable effects, in particular on the skin and / or on the environment.

According to the invention, a substance is “volatile” when its boiling point is less than 250 ° C. at atmospheric pressure. The “non-volatile” compounds have a boiling point greater than 250 ° C. at atmospheric pressure.

• * 70% à 94%, de préférence 70% à 90%, d'eau
• • 1% à 15%, de préférence 5% à 12%, d'au moins une substance hydrophobe parfumante,
• • 4% à 20%, de préférence 4% à 18%, d'au moins un solvo-surfactif, de préférence volatil, qui est un dérivé de glycérol monoalkylé de formule (I) suivante :
  
  dans laquelle le groupe « Alkyle » est un groupe alkyle linéaire comprenant 5 atomes de carbone, et R et R' sont chacun indépendamment H ou un groupe alkyle linéaire ou ramifié comprenant de 1 à 5 atomes de carbone, de préférence un groupe méthyle ou éthyle, à la condition que R est différent de R'.
• • 0,1% à 15%, de préférence 1% à 13%, d'au moins un tensioactif anionique et d'au moins un alkylglucoside en tant qu'agent hydrotrope.

The present invention therefore relates to a microemulsion of oil-in-water type comprising, preferably consisting of, by weight relative to the total weight of microemulsion:

• * 70% to 94%, preferably 70% to 90%, water
• • 1% to 15%, preferably 5% to 12%, of at least one hydrophobic perfume substance,
• • 4% to 20%, preferably 4% to 18%, of at least one solvo-surfactant, preferably volatile, which is a monoalkylated glycerol derivative of the following formula (I):
  
  wherein the "Alkyl" group is a linear alkyl group comprising 5 carbon atoms, and R and R 'are each independently H or a linear or branched alkyl group comprising from 1 to 5 carbon atoms, preferably a methyl or ethyl group , provided that R is different from R '.
• • 0.1% to 15%, preferably 1% to 13%, of at least one anionic surfactant and at least one alkylglucoside as hydrotropic agent.

The term “microemulsion of the oil-in-water type” denotes a liquid system in which an oily (or hydrophobic) phase is dispersed in an aqueous (or hydrophilic) continuous phase, so as to form drops with a diameter of less than 100 nm. . Interface oil / water is stabilized by surfactant compounds. Preferably, the drops have a diameter of between 2 and 100 nm.

These microemulsions present drops which are invisible to the naked eye and to the optical microscope. They are transparent, at least translucent, unlike emulsions, which is a sought-after property in particular for perfume compositions.

The term “hydrophobic substance” denotes a pure substance or a mixture which is insoluble or very slightly soluble in water, by nature. One possible method for determining the hydrophobicity of substances is to measure their solubility in different solvents or the retention time on a chromatographic column (by high performance liquid chromatography HPLC) of said hydrophobic substance.

The hydrophobic substances according to the invention are perfuming, ie they are odoriferous and can be used in perfumes. The term “odoriferous substance” is intended to mean a substance which can be detected olfactively by a subject and / or by olfactometry, according to principles known to those skilled in the art. An example of a method allowing the detection of an odoriferous substance is described in the document EP 0003088 . Other techniques for detecting an odoriferous substance are applicable, such as gas chromatography, mass spectroscopy or even infrared absorption analysis techniques. By odoriferous substance is also meant a substance which diffuses an odor, preferably pleasant for at least 20% of people, in particular a perfume.

Preferably, the hydrophobic perfume substance is a natural or synthetic hydrophobic perfume substance, more preferably natural. More preferably, it is chosen from terpenes, essential oils and natural compounds exhibiting odoriferous properties (terpenoids), in particular chosen from aldehydes, esters, ketones, alcohols, phenols, alkenes and ethers.

The term “terpenes” denotes hydrocarbons whose basic element is isoprene, their crude formula comprising a number of carbons which is multiple of 5, in particular terpenes containing in particular 10 or 15 carbon atoms, used in perfumery.

By "terpenoids" is meant derivatives of terpenes, for example alcohols, phenols, ketones, aldehydes, esters or ethers.

Terpenes and terpenoids are contained in "essential oils", designating the concentrated liquid, very often fragrant, volatile, produced by plants. Essential oils are most often extracted from plant organs by hydrodistillation in particular, but the constituents of these oils are widely synthesized by industry.

• terpènes: pinènes, camphènes, limonène, cadinène, carène, caryophyllène,
• alcools : linalol, géraniol, menthol, citronellol,
• cétones: menthone, carvone, béta-ionone, thuyone, camphre, cyclopentadécanone,
• aldéhydes : citral, citrannal, citronellal, aldéhyde cinnamique, lilial,
• esters: acétate de linalyle, acétate de menthyle, acétate de géranyle, succinate de géranyle, phénols : thymol, carvacrol, eugénol, isoeugénol,
• éthers: anéthol, eucalyptol, cinéol, oxyde de rose,
• alcènes : limonène.

The following natural hydrophobic perfume substances can in particular be used:

• terpenes: pinenes, camphenes, limonene, cadinene, carene, caryophyllene,
• alcohols: linalool, geraniol, menthol, citronellol,
• ketones: menthone, carvone, beta-ionone, thujone, camphor, cyclopentadecanone,
• aldehydes: citral, citrannal, citronellal, cinnamaldehyde, lilial,
• esters: linalyl acetate, menthyl acetate, geranyl acetate, geranyl succinate, phenols: thymol, carvacrol, eugenol, isoeugenol,
• ethers: anethole, eucalyptol, cineol, rose oxide,
• alkenes: limonene.

Essential oils can be ylang-ylang, bergamot, eucalyptus, lavender, lavandin, lemongrass, patchouli, peppermint, pine, rose, coriander, Shiu, sage , geranium, palmarosa, LitseaCubeba, lemon, lemongrass, orange blossom, grapefruit, lime, tangerine, tangerine, orange, cajeput, camphor, rosemary, anise green, star anise, fennel, basil, tarragon, cloves, chili, thyme, sassafras, wormwood, mugwort, cedar, hyssop, tagetes, rue, elemi, galbanum, juniper berries, cabreuva, gaiac wood, sandalwood, vetiver, ambrette, angelica, iris rhizome, carrot, celery, cumin , lovage, parsley, cinnamon, cardamom, ginger, nutmeg, pepper, olibanum, myrrh, Peruvian balsam, styrax, buchu, chamomile or cistus (Jean Garnero , "Essential oils", Engineering techniques nieur, Treatise on physico-chemical constants, K-345).

The amount of hydrophobic perfume substance in the microemulsions of the invention is from 1% to 15% by weight, preferably from 5% to 12% by weight relative to the total weight of microemulsion.

The term “solvo-surfactant” denotes an amphiphilic compound, combining certain properties of surfactants, in particular the reduction in water / air surface tensions and oil / water interfaces, the ability to self-associate in water, and certain properties of solvents, including the ability to evaporate without leaving residue.

Surprisingly, the Applicant has discovered and demonstrated that the use of a solvo-surfactant of formula (I) as defined in claim 1 made it possible to obtain a stable perfuming composition which is transparent or at least translucent. , which includes a large amount of perfume and as little surfactant as possible.

dans laquelle le groupe « Alkyle » est un groupe alkyle linéaire comprenant 5 atomes de carbone, et R et R' sont chacun indépendamment H ou un groupe méthyle ou éthyle, à la condition que R est différent de R'.The solvo-surfactant present in the microemulsion of the invention is the monoalkylated glycerol derivative of formula (I) as defined above, namely:

wherein the "Alkyl" group is a linear alkyl group comprising 5 carbon atoms, and R and R 'are each independently H or a methyl or ethyl group, provided that R is other than R'.

The monoalkylated glycerol derivative of formula (I) in which the "Alkyl" group is a linear alkyl group comprising 3 carbon atoms (propyl group), R is H and R 'is methyl, is 1-methoxy-3-propoxypropan -2-ol. It is called “C301” in the examples of the present application.

The monoalkylated glycerol derivative of formula (I) in which the "Alkyl" group is a linear alkyl group comprising 3 carbon atoms (propyl group), R is methyl and R 'is H, is 2-methoxy-3-propoxypropan -1-ol. It is called “C310” in the examples of the present application.

The monoalkylated glycerol derivative of formula (I) in which the "Alkyl" group is a linear alkyl group comprising 4 carbon atoms (butyl group), R is H and R 'is methyl, is 1-methoxy-3-butoxypropan -2-ol. It is called “C401” in the examples of the present application.

The monoalkylated glycerol derivative of formula (I) in which the "Alkyl" group is a linear alkyl group comprising 4 carbon atoms (butyl group), R is methyl and R 'is H, is 2-methoxy-3-butoxypropan -1-ol. It is called “C410” in the examples of the present application.

The monoalkylated glycerol derivative of formula (I) in which the "Alkyl" group is a linear alkyl group comprising 5 carbon atoms (pentyl group), R is H and R 'is methyl, is 1-methoxy-3-pentoxypropan-2-ol. It is called “C501” in the examples of the present application.

The monoalkylated glycerol derivative of formula (I) in which the "Alkyl" group is a linear alkyl group comprising 5 carbon atoms (pentyl group), R is methyl and R 'is H, is 2-methoxy-3-pentoxypropan -1-ol. It is called “C510” in the examples of the present application.

More preferably, the solvo-surfactant present in the microemulsion of the invention is the monoalkylated glycerol derivative of formula (I) as defined above in which the “Alkyl” group is a linear alkyl group comprising 5 carbon atoms. This compound is 2-methoxy-3-pentoxypropan-1-ol, called "C510".

The amount of volatile solvo-surfactant in the microemulsion of the invention is from 4% to 20% by weight, preferably from 4% to 18% by weight, and even more preferably from 4% to 10% by weight.

The term “surfactant” denotes a compound of amphiphilic nature, non-volatile, comprising a hydrophilic and polar part, and an apolar hydrophobic part. A surfactant lowers the surface tension of aqueous solutions and lowers the interfacial tension between water and an immiscible organic liquid. It thus makes it possible to dissolve two immiscible phases, such as water and oil, by interacting through its polar part with water and by its non-polar part with oil.

The surfactant present in the microemulsion according to the invention is an anionic surfactant, namely a surfactant whose hydrophilic part is negatively charged. Anionic surfactants have been shown to be the most effective, in the context of the invention, compared with nonionic, amphoteric or cationic surfactants. For the purposes of the invention, the term “more effective” should be understood to mean an introduction of surfactant in a smaller amount to form a microemulsion.

• les alkylsulfonates, et notamment :
  • le sodium C14-17 sulfonate (SAS),
  • le sulfosuccinate de dihexyle (DHS) de formule :
    
    dans laquelle M⁺ représente Na⁺, K⁺, NH₄ ⁺, (HOCH₂CH₂)₃NH⁺, ou
  • le sulfosuccinate d'éthyl-2-hexyle (Aérosol OT® ou AOT de chez CYTEC) de formule :
    
    dans laquelle M⁺ représente Na⁺, K⁺, NH₄ ⁺, (HOCH₂CH₂)₃NH⁺,
• les alkylarylsulfonates de formule :
  
  dans laquelle w est un entier compris de 8 à 12,
  et notamment l'isooctylbenzènesulfonate de sodium, l'isononyl benzènesulfonate de sodium ou l'isododécylbenzènesulfonate de sodium de formule :
  
• les propoxysulfates de formule :
  
  dans laquelle le nombre de motifs propoxylate n est compris de 4 à 8,
• les alkylsulfates, notamment les sels du sulfate de lauryle tel que le lauryl sulfate de sodium encore dénommé dodécyl sulfate de sodium (SDS), le lauryl sulfate d'ammonium (ALS) ; les alkyléther sulfates de sodium tel que le lauryléther (laureth) sulfate de sodium (LES) ; le sodium coco sulfate (SCS),
• et les sels d'acides gras de formule R-CO2^- M⁺, dans laquelle R représente une chaîne carbonée, linéaire ou ramifiée, saturée ou insaturée, contenant 8 à 18 atomes de carbone, et M⁺ représente un cation choisi parmi les ions Na⁺, K⁺, NH₄ ⁺, (HOCH₂CH₂)₃NH⁺, notamment le sel d'acide oléique de formule CH₃(CH2)₇CH=CH(CH₂)₇CO₂ ^- M⁺ dans lequel M⁺ a les significations définies ci-dessus.

According to an advantageous embodiment, the anionic surfactant present in the microemulsion of the invention is chosen from:

• alkylsulfonates, and in particular:
  • sodium C14-17 sulfonate (SAS),
  • dihexyl sulfosuccinate (DHS) of the formula:
    
    in which M ⁺ represents Na ⁺ , K ⁺ , NH ₄ ⁺ , (HOCH ₂ CH ₂ ) ₃ NH ⁺ , or
  • ethyl-2-hexyl sulfosuccinate (Aerosol OT® or AOT from CYTEC) of formula:
    
    in which M ⁺ represents Na ⁺ , K ⁺ , NH ₄ ⁺ , (HOCH ₂ CH ₂ ) ₃ NH ⁺ ,
• alkylarylsulphonates of formula:
  
  where w is an integer from 8 to 12,
  and in particular sodium isooctylbenzenesulphonate, sodium isononyl benzenesulphonate or sodium isododecylbenzenesulphonate of formula:
  
• propoxysulphates of formula:
  
  in which the number of propoxylate units n is from 4 to 8,
• alkyl sulphates, in particular salts of lauryl sulphate such as sodium lauryl sulphate also called sodium dodecyl sulphate (SDS), ammonium lauryl sulphate (ALS); sodium alkyl ether sulfates such as sodium lauryl ether (laureth) sulfate (LES); sodium coconut sulfate (SCS),
• and salts of fatty acids of formula R-CO2 ^- M ⁺ , in which R represents a carbon chain, linear or branched, saturated or unsaturated, containing 8 to 18 carbon atoms, and M ⁺ represents a cation chosen from ions Na ⁺ , K ⁺ , NH ₄ ⁺ , (HOCH ₂ CH ₂ ) ₃ NH ⁺ , in particular the oleic acid salt of formula CH ₃ (CH2) ₇ CH = CH (CH ₂ ) ₇ CO ₂ ^- M ⁺ in which M ⁺ has the meanings defined above.

The microemulsion comprises an alkyl glucoside as a hydrotropic agent. By “hydrotropic agent” is meant an amphiphilic compound, comprising hydrophilic functional groups, used to allow the solubilization of poorly soluble substances in an aqueous solution.

Surprisingly, the Applicant has demonstrated that the combination of at least one anionic surfactant and of at least one alkylglucoside makes it possible to increase the cloud point of the microemulsion.

By cloud point according to the invention is meant the temperature above which the microemulsion changes from a transparent (or even translucent) state to a cloudy or even milky state. The microemulsion according to the invention must maintain stability under conventional conditions of use and in fact must be stable, and therefore remain transparent or even translucent, in a temperature range of between 5 ° C and 45 ° C inclusive.

Thus, thanks to a judicious combination of surfactant and alkylglucoside, it is possible to obtain a stable microemulsion using a very small amount of surfactant. Microemulsions containing only the surfactant alone, or containing only the alkylglucoside alone, in equivalent or almost equivalent amounts are, on the other hand, not stable. There is therefore a synergistic effect between the anionic surfactant and the alkylglucoside.

In addition, this synergistic effect also has a positive impact on the amount of solvo-surfactant introduced into the microemulsion. Thus, thanks to the joint use of anionic surfactant and of alkylglucoside, it is possible to use quantities of lower solvosurfactants, namely ranging from 4% to 10% by weight relative to the total weight of the microemulsion. In the examples below, an amount of 5% of solvo-surfactant makes it possible to obtain a stable microemulsion and perfect solubilization of the hydrophobic perfume substance. The decrease in the amount of solvo-surfactant is done in favor of the amount of water which can thus be increased. The aqueous character of the microemulsion is thus increased.

According to an advantageous embodiment, the alkyl glucoside present in the microemulsion of the invention is chosen from heptyl glucoside, octyl glucoside, decyl glucoside and their mixtures, and is preferably heptyl glucoside.

The amount of anionic surfactant and of alkylglucoside present in the microemulsion of the invention is from 0.1% to 15% by weight, preferably from 1% to 13% by weight relative to the total weight of microemulsion.

• la quantité de tensioactif anionique est inférieure ou égale à 2% en poids par rapport au poids total de microémulsion,
• la quantité d'alkylglucoside est de 0,5% à 13% en poids par rapport au poids total de microémulsion, et de préférence de 0,5% à 8%.

More particularly, in the microemulsion of the invention:

• the amount of anionic surfactant is less than or equal to 2% by weight relative to the total weight of microemulsion,
• the amount of alkylglucoside is from 0.5% to 13% by weight relative to the total weight of microemulsion, and preferably from 0.5% to 8%.

According to an advantageous embodiment of the invention, the ratio of anionic surfactant: alkylglucoside is from 1: 4 to 1: 12, and preferably from 1: 4 to 1: 10.

• 70% à 90% d'eau,
• 5% à 12% d'au moins une substance hydrophobe parfumante,
• 4% à 18% d'au moins un solvo-surfactif volatil,
• 1% à 13%, d'au moins un tensioactif anionique et d'au moins un alkylglucoside en tant qu'agent hydrotrope.

Preferably, the microemulsion according to the invention consists of:

• 70% to 90% water,
• 5% to 12% of at least one hydrophobic perfume substance,
• 4% to 18% of at least one volatile solvo-surfactant,
• 1% to 13%, of at least one anionic surfactant and at least one alkyl glucoside as hydrotropic agent.

Preferably, the microemulsion according to the invention is substantially free of ethanol, ie it comprises less than 3% by weight of ethanol, preferably less than 2% by weight of ethanol, preferably less than 1% by weight of ethanol. More preferably, it is free of ethanol, ie it contains 0% by weight of ethanol.

The microemulsion according to the invention makes it possible in particular to obtain an aqueous perfuming composition having a transparency similar to an alcoholic product, without a greasy or sticky feel, and which does not leave traces or residues on the tissues or the skin.

Optionally, the microemulsion according to the invention can comprise from 0.01% to 2% by weight of at least one additive.

• un agent anti-mousse choisi parmi le décaméthyl cyclopentasiloxane, la diméthicone, le cétyl diméthicone, le diméhicone copolyol, le diméthiconol, l'hexaméthyldisiloxane, l'hexamidine diiséthionate, l'hexyl alcohol, l'hexyldeceth-2, l'isopropyl alcohol, le phénethyl disiloxane, le phényl triméthicone, le polysilicone-10, le polysilicone-7, le polysilicone-8, le propyl alcohol, le silica diméthyl silylate, le silica silylate, le siméthicone, le tetraméthyl decynediol et le triméthylsiloxysilicate;
• un conservateur choisi par exemple parmi le sodium benzoate, le potassium benzoate, le sodium salicylate, le caprylyl glycol, le pentylène glycol, l'éthylhéxylglycerine, le chlorphénesine, la chlorhexidine, le chlorhexidine digluconate, le méthylisothiazolinone, le méthylparaben, le propylparaben, le phénéthyl alcohol et le phénoxyethanol;
• un antioxydant choisi par exemple parmi le BHA, le BHT et le tocophérol.

According to a preferred embodiment, the microemulsion according to the invention can comprise, without limitation, one or more of the following additives:

• an anti-foaming agent chosen from decamethyl cyclopentasiloxane, dimethicone, cetyl dimethicone, domevehone copolyol, dimethiconol, hexamethyldisiloxane, hexamidine diisethionate, hexyl alcohol, hexyldeceth-2, isopropyl alcohol, phenethyl disiloxane, phenyl trimethicone, polysilicone-10, polysilicone-7, polysilicone-8, propyl alcohol, silica dimethyl silylate, silica silylate, simethicone, tetramethyl decynediol and trimethylsiloxysilicate;
• a preservative chosen for example from sodium benzoate, potassium benzoate, sodium salicylate, caprylyl glycol, pentylene glycol, ethylhexylglycerine, chlorphenesine, chlorhexidine, chlorhexidine digluconate, methylisothiazolinone, methylparaben, propylparaben, phenethyl alcohol and phenoxyethanol;
• an antioxidant chosen, for example, from BHA, BHT and tocopherol.

The microemulsions according to the invention have a fragrance quality that is stable over time corresponding to the standard shelf life of a cosmetic product, and temperature stable from 5 to 45 ° C., which corresponds to the exposure and exposure temperatures. use of a cosmetic product.

• la capacité d'une composition parfumée à maintenir, après application, un seuil de perception olfactif dans le temps,
• la capacité d'une composition à maintenir, une fois appliquée, sa forme olfactive dans le temps,
• la capacité d'une composition à ne pas subir d'altérations endogènes ou exogènes, qui pourraient modifier sa forme olfactive, et
• l'innocuité, qui est la faculté d'une composition à ne pas produire d'effets indésirables une fois appliquée sur la peau de l'utilisateur.

The technical criteria for the quality of a fragrance, in the case of an aqueous fragrance, are:

• the ability of a scented composition to maintain, after application, an olfactory perception threshold over time,
• the ability of a composition to maintain, once applied, its olfactory form over time,
• the ability of a composition not to undergo endogenous or exogenous alterations, which could modify its olfactory form, and
• harmlessness, which is the ability of a composition not to produce undesirable effects once applied to the user's skin.

Very advantageously, the microemulsions of the invention are thermodynamically stable and have a transparent or translucent appearance and even more advantageously, the microemulsions of the invention are thermodynamically stable and have a transparent or translucent appearance for at least one or two years.

• la parfumerie fine, ou
• la cosmétique et les produits d'hygiène corporelle.

The microemulsions of the invention are advantageously used for the preparation of compositions applied to:

• fine perfumery, or
• cosmetics and personal hygiene products.

Thus, the present invention also relates to the use of a microemulsion according to the invention, for the preparation of a fine perfumery composition, or of a cosmetic or body hygiene composition.

Microemulsions can be used in cosmetics. They can then contain in particular, and without this list being limiting, one or more of the compounds chosen from silicones, paraffin oil, isooctane, isodecane, squalene, squalane, sebum and lanolin.

Propylglycérolmonométhylé C310

Butylglycérolmonométhylé C401

Butylglycérolmonométhylé C410

Pentylglycérolmonométhylé C501

Pentylglycérolmonométhylé C510

In the examples which follow, the names, abbreviations and structures of the solvo-surfactants tested, namely the monomethylated glycerol derivatives (I), are as follows: NAMES ABBREVIATIONS STRUCTURES Propylglycerolmonomethyl C301

Propylglycerolmonomethyl C310

Butylglycerolmonomethyl C401

Butylglycerolmonomethyl C410

Pentylglycerolmonomethyl C501

Pentylglycerolmonomethyl C510

Example 1: Synthesis of the solvo-surfactants according to the invention, the monomethylated glycerol derivatives of formula (I)

The syntheses of 1-methoxy-3-propoxypropan-2-ol (C301) and 1-methoxy-3-pentoxypropan-2-ol (C501) are carried out in two stages. The synthesis of 1-methoxy-3-butoxypropan-2-ol (C401) is carried out simply by opening the epoxide insofar as the starting reagent, butylglycidol, is commercially available.

a) Condensation of alcohol on epichlorohydrin

The condensation of the alcohol (1 mole) on the epichlorohydrin takes place in a slight excess of epichlorohydrin (1.5 moles) in the presence of ZnCl ₂ as catalyst. The epichlorohydrin is added dropwise over 1 hour at 100 ° C. The reaction medium is then maintained at 115 ° C for 5 h then cooled to 50 ° C. A dropwise addition over 1 hour of 48% NaOH (2.3 mol) is then carried out. All these synthesis steps are carried out with vigorous stirring. Once the reaction is complete, distilled water is added and the product is thus washed twice with water to remove the residual salts.

Synthesis of C _n glycidol, where n = 3.4.5

The product obtained is finally distilled under vacuum at 10-20 mbar between 75 and 80 ° C.

b) Opening of the epoxy with the methanolate

C _n glycidol (where n = 3, 4, 5) is added dropwise to a methanol solution containing sodium methanolate previously obtained by reaction between methanol and solid sodium. The addition is carried out at reflux at 80 ° C. for 30 min, then the temperature of 80 ° C. is maintained for 24 hours until complete disappearance of C _n glycidol:

Opening of the epoxide by sodium methanolate Purification:

The methanol is evaporated off on a rotary evaporator once the reaction is complete. The product obtained is then washed with two saturated aqueous NaCl solutions: one containing 3.4% of HCl and the other containing 10% of NaHVCO ₃ .

c) Synthesis of compounds C310, C410, and C510

The synthesis of compounds C310, C410 and C510 is carried out in three steps from C _n glycidol (where n = 3, 4, 5) as described in scheme 1 below.

The first step is carried out under the conditions of step b) described above, replacing the methanol with benzyl alcohol. In a second step, the intermediate thus obtained is reacted in a basic medium in the presence of dimethyl sulphate in order to obtain the methylation of the free secondary alcohol function. After a third step of catalytic hydrogenation in the presence of hydrogen and palladium on carbon, the final product is obtained.

Synthesis of C310, C410 and C510 solvo-surfactants Example 2: Solubilization of perfume concentrates Solubilization by solvo-surfactants alone Solubilization of gamma-undecalactone perfume

The aim of this test is to classify the solvo-surfactants according to their capacity to solubilize (or not) gamma-undecalactone.

Formulas containing 5% gamma-undecalactone, 4.4% SDS (anionic surfactant), X% solvo-surfactant and QSP on water were produced.

The table below details the amount of SS necessary to dissolve the perfume. C510 C501 C401 C410 C310 9.1% 9.3% 12.2% 16.2% 20%

The following classification is obtained: C510> C501> C401> C410> C310.

The solvo-surfactant with the best ability to dissolve the hydrophobic perfume substance is C510.

Example 3: Temperature stability of aqueous perfuming microemulsions

The following perfume juice (P) has been prepared: Perfume name CASE # Amount (%) UNDECALACTONE GAMMA 104-67-6 0.62 CIS 3 HEXENYL ACETATE 3681-71-8 1.21 HEXENYL CIS 3 BENZOATE 25152-85-6 2.42 EUGENOL 97-53-0 2.42 IONONE BETA 14901-07-6 3.64 METHYLIONONE GAMMA 127-51-5 6.06 BENZYL PROPIONATE 122-63-4 1.21 BENZYL ACETATE 140-11-4 6.06 HEDIONE HC 24851-98-7 36.36 ISO GAMMA SUPER 68155-66-8 31.52 Cis 3 HEXENYL SALICYLATE 65405-77-8 6.06 VANILIN 121-33-5 2.42

Then the following formulations were prepared: Formulation Water Perfume (P) Solvo-surfactant (C510) Surfactant ( SDS) Alkylglucoside ( Heptyl-glucoside) Stability 5 ° C to 45 ° C TO 80.4% 5% 12.5% 2.1% NO KO B 78.9% 5% 15% NO 1.1% KO VS 76.7% 5% 15% 2.0% 1.3% OK D 85.34% 5% 5% 0.66% 4.0% OK E 85.0% 5% 5% NO 5.0% KO

To be acceptable, formulations A, B, C, D and E must be temperature stable over a range of 5 ° C to 45 ° C.

The formulations are therefore placed in a bath at 5 ° C. and at 45 ° C., for 24 hours.

After observation, clear formulations are considered stable and cloudy formulations are considered unstable. The above table shows the stable compositions (“OK”) and the compositions which have led to destabilization (appearance of a cloudiness) (“KO”).

Only formulations C and D comprising a combination of an anionic surfactant and an alkylglucoside exhibit stability over the entire temperature range 5 ° C to 45 ° C.

Advantageously, composition D exhibits all the benefits of the invention thanks to the use of a judicious “surfactant: alkylglucoside” ratio which is 1: 6, making it possible to obtain an aqueous formulation rich in water (> to 85%) in the presence of a small amount of solvo-surfactant (5%).

Example 4 : Comparative test

A microemulsion of the invention, namely formulation D described in example 3 above, which comprises the solvo-surfactant C510, is compared with two other microemulsions (formulations D1 and D2) which respectively comprise hexylene glycol and propylene glycol in place of the solvo-surfactant C510.

Hexylene glycol and propylene glycol do not correspond to formula (I) of the solvo-surfactant of the invention. Formulation D (invention) D1 D2 Water 85.34% 85.34% 85.34% Perfume (P) 5% 5% 5% SDS 0.66% 0.66% 0.66% Heptyl glucoside 4% 4% 4% C510 5% - - Hexylene glycol - 5% - Propylene glycol - - 5%

The perfume juice P is as described in Example 3.

The heptyl glucoside used is that marketed by Seppic under the name “Sepiclear G7”.

The sodium lauryl sulfate (SDS) used is that marketed by BASF under the name "Texaplon LS30"

As already indicated, to be acceptable, formulations D, D1 and D2 must be temperature stable over a range of 5 ° C to 45 ° C.

The formulations are placed in a bath at 5 ° C. and at 45 ° C. for 24 hours.

After observation, clear formulations are considered stable and cloudy formulations are considered unstable.

It is thus observed that at D0, at room temperature, formulation D is clear while formulations D1 and D2 are already opalescent.

After 24 hours, both at 5 ° C and 45 ° C, formulations D1 and D2 are cloudy and a significant phase shift is observed, while formulation D of the invention has remained clear.

This comparative test therefore demonstrates the importance played by the solvo-surfactant of the invention.

Claims (9)

1. A microemulsion of oil-in-water type comprising by weight relative to the total weight of microemulsion:

   • 70% to 94%, preferably 70% to 90%, of water,

   • 1% to 15%, preferably 5% to 12%, of at least one hydrophobic fragrancing substance,

   • 4% to 20%, preferably 4% to 18%, of at least one preferably volatile solvo-surfactant, which is a monoalkylated glycerol derivative of following formula (I):

   

   wherein the "alkyl" group is a linear alkyl group comprising from 1 to 5 carbon atoms, and R and R' are each independently H or a linear or branched alkyl group comprising from 1 to 5 carbon atoms, preferably a methyl or ethyl group, with the proviso that R is different from R',

   • 0.1% to 15%, preferably 1% to 13%, of at least one anionic surfactant and of at least one alkyl glucoside as hydrotropic agent.
2. The microemulsion as claimed in claim 1, wherein the hydrophobic fragrancing substance is a natural hydrophobic fragrancing substance selected from terpenes, essential oils and natural compounds having odoriferous properties, especially selected from aldehydes, esters, ketones, alcohols, phenols, alkenes and ethers.
3. The microemulsion as claimed in any one of claims 1 to 4, wherein the anionic surfactant is selected from:

   • alkyl sulfonates, and in particular:

   - sodium C14-17 sulfonate (SAS),

   - dihexyl sulfosuccinate (DHS) of formula:

   

   wherein M+ represents Na⁺, K⁺, NH₄ ⁺, (HOCH₂CH₂)₃NH⁺, or

   - 2-ethylhexyl sulfosuccinate of formula:

   

   wherein M⁺ represents Na⁺, K⁺, NH₄ ⁺, (HOCH₂CH₂)_hNH⁺,

   • alkylaryl sulfonates of formula:

   

   wherein w is an integer from 8 to 12,
   and in particular sodium isooctylbenzenesulfonate, sodium isononylbenzenesulfonate or sodium isododecylbenzenesulfonate of formula:

   

   • propoxy sulfates of formula:

   

   wherein the number of propoxylate units n is from 4 to 8,

   • alkyl sulfates, especially salts of lauryl sulfate such as sodium lauryl sulfate also known as sodium dodecyl sulfate (SDS), ammonium lauryl sulfate (ALS); sodium alkylether sulfates such as sodium lauryl ether (laureth) sulfate (LES); sodium coco sulfate (SCS),

   • and salts of fatty acids of formula R-CO₂ ^- M⁺, wherein R represents a linear or branched, saturated or unsaturated carbon-based chain containing 8 to 18 carbon atoms, and M⁺ represents a cation selected from the ions Na⁺, K⁺, NH₄ ⁺, (HOCH₂CH₂)₃NH⁺, especially the oleic acid salt of formula CH₃(CH₂)₇CH=CH(CH₂)₇CO₂ ^- M⁺, wherein M⁺ has the above-defined meanings.
4. The microemulsion as claimed in any one of claims 1 to 3, wherein the alkyl glucoside is in particular selected from heptyl glucoside, octyl glucoside, decyl glucoside and mixtures thereof, and is preferably heptyl glucoside.
5. The microemulsion as claimed in any one of claims 1 to 4, wherein:

   - the amount of anionic surfactant is less than or equal to 2% by weight relative to the total weight of microemulsion,

   - the amount of alkyl glucoside is from 0.5% to 13% by weight relative to the total weight of microemulsion, and preferably from 0.5% to 8%.
6. The microemulsion as claimed in any one of claims 1 to 5, wherein the anionic surfactant: alkyl glucoside ratio is from 1:4 to 1:12, and preferably from 1:4 to 1:10.
7. The microemulsion as claimed in any one of claims 1 to 6, wherein the amount of solvo-surfactant is from 4% to 10% by weight relative to the total weight of microemulsion.
8. The microemulsion as claimed in any one of claims 1 to 7, which is substantially free of ethanol, preferably which is devoid of ethanol.
9. The use of a microemulsion as claimed in any one of claims 1 to 8 for the preparation of a fine fragrance composition or of a cosmetic or body hygiene composition.